Antibiotic treatment of age-related macular degeneration

ABSTRACT

A method is provided for the treatment of age-related macular degeneration by administering various antibiotics, such as tetracycline and its derivatives, rifamycin and its derivatives, macrolides, and metronidazole, to a patient in a therapeutically effective amount.

This is a continuation of application Ser. No. 09/072,521, filed May 4, 1998, now U.S. Pat No. 6,015,803.

TABLE OF CONTENTS

1. BACKGROUND OF THE INVENTION

1.1 TECHNICAL FIELD

1.2 BACKGROUND OF ART

2. SUMMARY OF THE INVENTION

3. BRIEF DESCRIPTION OF THE DRAWINGS

4. DESCRIPTION OF PREFERRED EMBODIMENTS

5. CLAIMS

6. ABSTRACT OF THE DISCLOSURE

7. DRAWING

8. DECLARATION AND POWER OF ATTORNEY

9. DECLARATION OF SMALL ENTITY STATUS

1. BACKGROUND OF THE INVENTION

1.1 Technical Field

The present invention is directed to the treatment of age-related macular degeneration (ARMD) by the administration of certain antibiotics. In one embodiment, broad-spectrum bacteriostatic antibiotics, such as tetracycline-based antibiotics (TBA), are administered for up to fourteen (14) months, which leads to measurable improvements in some of the symptoms.

1.2 Background of Art

Age-related macular degeneration (ARMD) is the leading cause of blindness among persons over fifty in the United States and other countries (Bressler NM et al., Age-related macular degeneration. Surv. Ophthalmol. 1988; 32:375-413). Two forms of age-related macular degeneration are known: (1) neovascular, also known as exudative, age-related macular degeneration (E-ARMD) and (2) nonneovascular, also known as nonexudative, age-related macular degeneration (NE-ARMD). NE-ARMD is characterized by the presence of drusen, yellow-white lesions of the retinal pigment epithelium within the macula, and by other abnormalities of the retinal pigment epithelium, including retinal cell death.

Although the exact etiology of ARMD is not known, several risk factors seem to be important for the manifestation of this disease. For example, ARMD may be caused by chronic exposure of the retina to light. The presence or absence of certain nutrients in the diet, such as the antioxidant vitamins E and C, also may affect one's predisposition for ARMD. Other conditions, such as hypertension and smoking, are also considered to be important risk factors for the development of this disease.

Recent histopathologic studies show that leukocytes and chronic inflammation may play a role in the pathogenesis of atrophic NE-ARMD (Penfold PL et al., Senile macular degeneration: The involvement of giant cells in the atrophy of the retinal pigment epithelium. Invest. Ophthalmol. Vis. Sci. 1986; 27:364-371) and E-ARMD (Penfold PL et al., Age-related macular degeneration: Ultrastructural studies of the relationship of leucocytes to angiogenesis. Graefe's Arch. Ophthalmol. 1987; 2256:70-76).

Several therapeutic methods have been tried. For example, vitamins and dietary supplements have been used for the purpose of delaying the onset of disease. Thalidomide is being investigated to determine if it will slow down or arrest new vessel formation. Laser or radiation has been used to destroy new vessels. However, none of these methods has led to successful results and no definitive treatment for ARMD has been developed to date.

2. SUMMARY OF THE INVENTION

The present invention is directed to the treatment of both E-ARMD and NE-ARMD by the long-term administration of antibiotics in therapeutically effective dosages which are safe for such prolonged usages. In one embodiment, a broad-spectrum, bacteriostatic antibiotic, such as tetracycline (250-1000 mg per day) is orally administered for six (6) weeks to fourteen (14) months.

Tetracyclines are broad spectrum bacteriostatic antibiotics known to have “collagenase inhibition properties, anti-oxidant activity, inhibition of protein synthesis in rapidly dividing cells, perturbation of leukocyte functions, interference with lymphocyte proliferation and anti-inflammatory effects” (Tilley BC et al., Minocycline in rheumatoid arthritis. A forty-eight (48) week double blind placebo controlled trial. MIRA trial Group. Annals of Internal Medicine. 1995; 122(2):81-89). Forty-eight (48) week therapy with TBA has been shown to moderate the signs and symptoms of inflammatory diseases such as rheumatoid arthritis (Tilley BC et al., Minocycline in rheumatoid arthritis. A forty-eight (48) week double blind placebo controlled trial. MIRA trial Group. Annals of Internal Medicine. 1995; 122(2):81-89). Its limited toxicity has enabled it to be used chronically as therapy for diverse diseases including acne rosacea (Brown SI et al., Diagnosis and treatment of ocular rosacea. Ophthalmology. 1978; 85:779-786) which is commonly seen in the elderly. Animal studies reveal that intravenous tetracycline achieves high concentrations in the uvea and retina (Salamon SM, Tetracyclines in ophthalmology. Surv. Ophthalmol. 1985; 29:265-275).

In addition to tetracycline, other antibiotics may be used, including tetracycline derivatives, such as minocycline, doxycycline, and oxycycline, but most preferably minocycline (100-200 mg per day); rifamycin and its derivatives, such as rifabutin (150-300 mg per day) and rifampin (150-300 mg per day), but most preferably rifabutin; macrolides, such as azithromycin, erythromycin, and clarithromycin, but most preferably azithromycin (250-500 mg per day) and erythromycin (400-1200 mg per day as ethyl succinate); and metronidazole (375 mg per day). Furthermore, antibiotics can be administered orally or parenterally, including intravenously, intramuscularly, or subcutaneously, as the case may be for the particular antibiotic and the modes of administration of these clinically recognized antibiotics are already set in the literature.

The invention is based, in part, on the discovery that the administration of certain antibiotics, especially tetracycline-based antibiotics (TBA), to individuals with ARMD for unrelated non-ocular diseases for a period of up to fourteen (14) months, led to measurable improvements in visual acuity and in peripheral fields when there was such loss.

3. BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing the study results wherein initial (before the treatment) vs. final (12 months after the commencement of treatment) acuity of studied eyes (n=20) is plotted. Numbers on or above diagonal dotted line represent number of eyes which improved two or more Snellen lines.

4. DESCRIPTION OF PREFERRED EMBODIMENTS

In a retrospective study, ten (10) patients with grade 3 or grade 4 (Bressler NM et al., The grading and prevalence of macular degeneration in Chesapeake By waterman. Arch. Ophthalmol. 1989; 107:847-852) NE-ARMD and a varied medical history including chronic rheumatoid arthritis, acne rosacea, or chronic dermatitis without keratitis, were treated with either tetracycline (250 mg, b.i.d.) or minocycline (100 mg, q.d.) for up to fourteen (14) months for treatment of the non-ocular diseases. Visual acuity was followed for up to fourteen (14) months or average twelve (12) months. All individuals had received initial ophthalmologic examinations, including fluorescein angiography which revealed ARMD only. No individual exhibited corneal or intra-ocular inflammatory diseases. The study included 6 females and 4 males and the average age was 79 years old.

Forty percent of the eyes demonstrated improvements in visual acuity, being equal to or greater than two Snellen lines, when measured twelve (12) months after the commencement of treatment. This percentage was significantly greater (p<0.05) than the four percent of NE-ARMD patients who spontaneously exhibited equivalent improvements (Smiddy W. E. et al., Prognosis of patients with bilateral macular drusen. Ophthalmology 1984; 91:271-276). Improvements were gradual, occurring only after three (3) to six (6) months of therapy. There were no detectable funduscopic changes. The vision of two patients deteriorated after stopping therapy for two (2) to three (3) months and subsequently improved again upon resuming therapy. Two eyes demonstrated visual field improvements.

The results, as shown in FIG. 1., suggest that the improvements in vision were produced by the TBA affecting the ARMD. The absence of corneal disease and the protracted course of gradual improvement make it unlikely that we were treating ocular acne rosacea. All acne rosacea patients treated by Brown and Shahinian showed an improvement within three (3) weeks of starting TBA therapy (Brown SI et al., Diagnosis and treatment of ocular rosacea. Ophthalmology 1978; 85:779-786). We are not aware of any retinal manifestations of acne rosacea or that chronic rheumatoid arthritis and acne rosacea are risk factors for ARMD. The literature reveals no reports similar to this study. 

What is claimed is:
 1. A method for the treatment of age-related macular degeneration, comprising systemically administering a therapeutically effective but safe amount of an antibiotic for a prolonged period of time to a patient in need thereof, wherein said antibiotic is selected from the group consisting of macrolides, rifamycin and its derivatives, and metronidazole.
 2. The method according to claim 1, wherein the antibiotic is rifamycin.
 3. The method according to claim 2, wherein the rifamycin is rifampin.
 4. The method according to claim 3, wherein the rifampin is orally administered in a dosage between 150 and 300 mg per day.
 5. The method according to claim 3, wherein the rifampin is administered for at least six weeks.
 6. The method according to claim 2, wherein the antibiotic is rifabutin.
 7. The method according to claim 6, wherein the rifabutin is orally administered in a dosage between 150 and 300 mg per day.
 8. The method according to claim 6, wherein the rifabutin is administered for at least six weeks.
 9. The method according to claim 1, the antibiotic is a macrolide.
 10. The method according to claim 9, the macrolide is erythromycin.
 11. The method according to claim 10, wherein the erythromycin is ethyl succinate.
 12. The method according to claim 11, wherein the erythromycin ethyl succinate is orally administered in a dosage between 400 and 1200 mg per day.
 13. The method according to claim 11, wherein the erythromycin ethyl succinate is administered for at least six weeks.
 14. The method according to claim 9, wherein the macrolide is azithromycin.
 15. The method according to claim 14, wherein the azithromycin is orally administered in a dosage between 250 and 500 mg per day.
 16. The method according to claim 14, wherein the azithromycin is administered for at least six weeks.
 17. The method according to claim 1, wherein the antibiotic is metronidazole.
 18. The method according to claim 17, wherein the metronidazole is orally administered at a dosage of 375 mg per day.
 19. The method according to claim 17, wherein the metronidazole is administered for at least six weeks. 